Exercise and hippocampal bidirectional synaptic plasticity

1999年，我们首次发现，自主运动可以增强成年海马体中新神经元的产生（称为成年神经发生），并促进空间记忆，海马体被认为支持认知功能。我在2001年获得了NSERC的最初资助，这使我得以在加拿大建立这项研究计划，并使用小鼠和大鼠，我们继续证明运动可以改变海马体的神经回路，并增强神经元相互交流的能力（这一过程称为突触功效的长期增强（LTP））。我们随后继续证明，运动也有利于现有的细胞，帮助神经元生长和发芽更多的分支和突触棘，就像肥料可以帮助植物生长和发育更多。这些结构上的改善也伴随着功能上的变化，使这些细胞更有能力与其他细胞交流，并提高了运动动物的学习和记忆能力。到目前为止，有相当多的证据表明，运动使海马体更有活力，提高学习能力，而不从事运动的动物的海马体在形态和功能上都更受限制和静态。我们目前的工作继续集中在检查允许运动有益于海马结构和功能的机制上，但是我们已经扩大了我们的重点，包括外周信号分子。 迄今为止，大多数焦点都集中在运动如何增强脑源性神经营养因子（BDNF），这是一种在新神经元的生长和分化中起重要作用的生长因子。虽然BDNF是介导运动效果的关键因素，但我们有新的证据表明，外周信号传导机制也可能通过影响BDNF发挥直接作用。我们的研究计划旨在探索与运动对肌肉和脂肪细胞（脂肪细胞）影响相关的两个信号级联。最近的研究表明，运动可以通过PGC-1 α/FNDC 5通路诱导BDNF表达。FNDC 5是一种小蛋白质或肌因子，在运动过程中从肌肉中释放出来。肌因子作为糖基化的1型膜蛋白分泌。FNDC 5的分泌形式被称为鸢尾素，我们有初步的数据表明鸢尾素可以直接影响海马中的突触可塑性。 脂联素是一种蛋白质激素，运动后由脂肪细胞分泌到血液中。脂联素受体在海马体中高度表达（即ADIPOR 1和ADIPOR 2），其活化导致AMPK（5'腺苷一磷酸活化蛋白激酶）磷酸化。AMPK参与调节BDNF的表达，我们认为BDNF的诱导可能与AMPK激活PGC 1-alpha信号的能力有关，这表明脂联素和运动过程中鸢尾素的释放之间存在联系。

In 1999 we showed for the first time that voluntary exercise can enhance the production of new neurons in the adult hippocampus (called adult neurogenesis) and facilitate spatial memory, a cognitive function that the hippocampus is believed to support. My initial NSERC funding in 2001 allowed me to establish this research program in Canada, and using both mice and rats, we went on to show that exercise can alter the neuro-circuitry of the hippocampus, and enhance the capacity for neurons to communicate with one another (a process called long-term potentiation (LTP) of synaptic efficacy). We subsequently went on to show that exercise also benefited existing cells, helping neurons to grow and sprout more branches and synaptic spines, much like fertilizer can help plants grow and develop more. These structural improvements were also accompanied by functional changes, making these cells more capable of communicating with other cells, and also improving learning and memory performance in the animals that exercised. Thus far, there is considerable evidence to indicate that exercise makes for a more dynamic hippocampus and enhances learning capacity, while animals that do not engage in exercise have a hippocampus that is both morphologically and functionally more restricted and static. Our current work continues to be focused on examining the mechanisms that allow exercise to be beneficial for hippocampal structure and function, however we have expanded our focus to include peripheral signaling molecules. Most of the focus to date has been on how exercise enhances brain-derived neurotrophic factor (BDNF), a growth factor that plays an important role in the growth and differentiation of new neurons. While BDNF is a key factor in mediating the effects of exercise, we have new evidence that indicates that peripheral signalling mechanisms also can play a direct role, possibly by affecting BDNF. Our research program intends to explore two signalling cascades related to the effects of exercise on muscle and adipocytes (fat cells). It has recently been shown that exercise can induce BDNF expression by acting though a PGC-1alpha/FNDC5 pathway. FNDC5 is a small protein, or myokine, that is released from muscles during exercise. Myokines are secreted as glycosylated type 1 membrane proteins. The secreted form of FNDC5 is called irisin, and we have preliminary data that irisin can directly impact synaptic plasticity in the hippocampus. Adiponectin, is a protein-hormone that is secreted from adipocytes into the bloodstream after exercise. Adiponectin receptors are highly expressed in the hippocampus (i.e. ADIPOR1 and ADIPOR2) and their activation leads to the phosphorylation of AMPK (5' adenosine monophosphate-activated protein kinase). AMPK is involved in regulating BDNF expression, and we believe that BDNF induction may be related to the ability of AMPK to activate PGC1-alpha signaling, suggesting a link between adiponectin and irisin release during exercise.